The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the point of interest is called the ‘absorbed dose’ or dose and the unit is given in gray (Gy) or J/kg. The dose can be calculated by knowing the energy of the radiation and the composition of the medium, which then leads to the formation of dosimeters. A dosimeter is defined as a device that when irradiated, exhibits a quantifiable and reproducible change in physical or chemical property of the device which can be related to the dose in a given material using appropriate analytical techniques.
Dosimetry plays an important role in process control in irradiation facility where documents are required to assure that all the factors which might influence the level of uncertainty in absorbed dose estimation, and precautions should be taken to minimize the uncertainties (ASTM. Standard Guide for Performance Characterization of Dosimeters and dosimetry Systems for Use in Radiation Processing. ASTM E2701). The importance of dosimetry is emphasized in the standards on radiation sterilization which are currently drafted by the European standards organization CEN and by the international standards organization ISO. In both standards, dosimetry plays key roles in characterization of the facility, in qualification of the process and in routine process control. As a function of the work on the standards, several issues are now receiving major attention. These include traceability and uncertainty limits of the dose measurements, calibration procedures, environmental influence and combination of influence factors such as dose rate and temperature. The increased attention to these factors has increased the demands on existing dosimeter systems, and need for more sensitive chemical composition to help these dosimeters.